From 505ea3771a80da355d60235a2ca9e81307f5eba3 Mon Sep 17 00:00:00 2001
From: Luke Else <mail@luke-else.co.uk>
Date: Thu, 14 Dec 2023 18:19:21 +0000
Subject: [PATCH] Day 14 Part 2 Complete -> First solution took agest to run
 but added the hashmap to detect cycles in the rotations. Thanks reddit :)

---
 src/solutions/day14.rs | 57 +++++++++++++++++++++++++++++++++++++++---
 1 file changed, 54 insertions(+), 3 deletions(-)

diff --git a/src/solutions/day14.rs b/src/solutions/day14.rs
index 40c4f5f..9d3a392 100644
--- a/src/solutions/day14.rs
+++ b/src/solutions/day14.rs
@@ -1,3 +1,5 @@
+use std::collections::HashMap;
+
 use super::Solution;
 
 pub struct Day14 {}
@@ -19,9 +21,28 @@ impl Solution for Day14 {
 
     fn part2(
         &self,
-        _input: &mut Vec<String>,
+        input: &mut Vec<String>,
     ) -> Result<Box<dyn std::fmt::Display + Sync>, Box<dyn std::error::Error>> {
-        Ok(Box::new("Ready"))
+        let mut rock_formation = input
+            .iter()
+            .map(|r| r.chars().collect::<Vec<_>>())
+            .collect::<Vec<_>>();
+
+        let mut rotations: HashMap<Vec<Vec<char>>, usize> = HashMap::new();
+        for i in 1..=1_000_000_000 {
+            for _ in 0..4 {
+                self.pull_north(&mut rock_formation);
+                rock_formation = self.rotate(&rock_formation);
+            }
+
+            if let Some(rotation) = rotations.insert(rock_formation.clone(), i) {
+                if (1_000_000_000 - i) % (i - rotation) == 0 {
+                    break;
+                }
+            }
+        }
+
+        Ok(Box::new(self.get_load(&rock_formation)))
     }
 
     fn get_day(&self) -> u8 {
@@ -59,6 +80,17 @@ impl Day14 {
             })
             .sum::<usize>() as u32
     }
+
+    // Function that rotates the given vector through 90 degrees clockwise
+    fn rotate(&self, cave: &Vec<Vec<char>>) -> Vec<Vec<char>> {
+        let mut new_cave = vec![vec![' '; cave.len()]; cave[0].len()];
+        for row in 0..cave.len() {
+            for col in 0..cave[0].len() {
+                new_cave[col][cave.len() - row - 1] = cave[row][col];
+            }
+        }
+        new_cave
+    }
 }
 
 /// Test from puzzle input
@@ -98,6 +130,25 @@ mod test {
             .unwrap()
             .to_string();
 
-        assert_eq!(answer, "Ready");
+        assert_eq!(answer, "64");
+    }
+
+    #[test]
+    fn rotation_test() {
+        let challenge = day14::Day14 {};
+
+        let mut arr = vec![
+            vec!['a', 'b', 'c', 'd'],
+            vec!['d', 'e', 'f', 'g'],
+            vec!['h', 'i', 'j', 'k'],
+            vec!['l', 'm', 'n', 'o'],
+        ];
+
+        let ans = arr.clone();
+        for _ in 0..4 {
+            arr = challenge.rotate(&arr);
+        }
+
+        assert_eq!(arr, ans);
     }
 }